The invention relates to a system and a method for telecommunications and, more specifically, to a system and a method for securing network resources requested for completing a telecommunications call.
A common concern in the telecommunications industry has been how to handle the situation in which a caller is unable to establish a connection to a called terminal, typically a telephone, because insufficient network resources are available to connect to the called terminal. For example, the called terminal might be a telephone which has a single line connecting the terminal to a central office. If a user of the called terminal is already on the line when a call is placed, the traditional approach has been to notify the calling party that the line to the called terminal is occupied by transmitting a busy signal to the terminal of the calling party.
A solution to the problem of a busy line is to employ a call waiting feature. A second call which is initiated when the called party is on the line with a first call causes the central office to transmit an audible signal, notifying the called party of the availability of the second call. If the called party triggers the appropriate signal to the central office, the called party""s line is switched over to the second call. However, the called party can choose to disregard the notice of the second call. Both the busy signal transmission and the call waiting feature provide only partial caller satisfaction to the occupied line problem. If a caller encounters a busy signal, the caller has no way of knowing how long the called party will remain on the line with the first call. The caller might have to retry the call numerous times before the line becomes available. In the call waiting scenario, if the called party ignores a call waiting tone, the caller might not be able to determine that the called party is actually utilizing the called terminal. In this case, the caller will not even know to retry the call, because the caller will not be notified that the called party is located at the called terminal.
A camp-on feature enables a caller to instruct a switching device, such as a central office (CO) or a private branch exchange (PBX), to monitor the line to the called terminal to determine when the called terminal becomes available. Upon determining that the line to the called terminal is no longer occupied, the switching device places the call to the called terminal and notifies the caller that the call has been placed. In this manner, the call is placed as soon as the called terminal becomes available, without the caller having to manually replace the call.
If a call attempt is unsuccessful, it is possible that the call was rejected because insufficient network bandwidth is available to support the call. That is, the called terminal might be available, but insufficient bandwidth prevents the call from being established to the called terminal. U.S. Pat. No. 5,812,551 to Tsukazoe et al. describes a system which is capable of camp-on request registration specifically for network bandwidth. A terminal that has been issued a connection refusal transmits a camp-on request to an Asynchronous Transfer Mode (ATM) exchange. The ATM exchange monitors an xe2x80x9cempty-bandxe2x80x9d value to determine bandwidth availability. When the empty-band value exceeds the band value required for the camp-on request, the ATM exchange establishes the connection.
Although the Tsukazoe et al. system works well for its intended purpose, further improvements are desired. A call attempt can be rejected for reasons other than an occupied line or insufficient bandwidth availability. What is needed is a system and a method for securing network resources in a manner which is responsive to the availability of multiple network resources required to complete a call.
A system and a method for securing necessary resources for establishing a call include a resource availability monitor which compares available levels of at least two network resources to requested levels of the network resources, as specified in a call setup signal. If insufficient network resources are available when the call request signal is received, a resource reservation mechanism requests reservation of the call-specified resources and a call setup subsystem automatically establishes the call when the available levels equal or exceed the required levels.
In a preferred embodiment, the invention is practiced in a voice-over-data-network environment. The system requests reservation of quantities of at least two network resources specified in the call request, monitors the available levels of the specified resources, reserves the resources as they become available, and when the requested levels of the network resources have been reserved, the call setup subsystem establishes the call. In this preferred embodiment, the network resources include Digital Signal Processor (DSP) resources, including transcoding DSP resources and conferencing DSP resources. The transcoding DSP resources are utilized, among other things, to perform conversion functions between terminals that utilize different compression algorithms. The conferencing DSP resources are utilized to mix simultaneously generated voice data within a conferencing call. The network resources further include trunking resources required to complete a call. For example, the system might include a gatekeeper that is connected to multiple trunks for supporting incoming and outgoing calls. The trunking resource requirements specified in a call request signal are compared to available trunking resources to determine whether reservation of trunking resources must be requested. Network bandwidth requirements are compared to network bandwidth availability and the availability of the called terminal is ascertained to determine whether reservation of network bandwidth or access to the called terminal must be requested.
In a preferred embodiment, after it is determined that the requested levels of the network resources are not available, the resource reservation mechanism forms a queue for the calls that require network resources which have availability levels which are below the requested quantities. For example, a conference call request might specify DSP requirements for a conferencing call which will include video teleconferencing to two called terminals. If network bandwidth requirements, trunking requirements, and called terminal access requirements exceed the availability levels for all three of these resources, the resource reservation mechanism places the call into queues for each of the resources. The call advances within the queues and, upon reaching the front of one of the queues, for example the network bandwidth queue, the resource reservation mechanism reserves the required bandwidth level for a predetermined time interval. If the call is not established within the predetermined time interval because, for example, sufficient DSP resources had not been secured within the time interval that started when the network bandwidth came available, the bandwidth is released to free up bandwidth for other calls. The precise duration of the network interval can be calibrated to accommodate the competing interests of minimizing the waiting period that calls must endure before all the required resources for a call can be simultaneously reserved and of minimizing wasted resources which are tied up while the resources are reserved.
In one embodiment, the method is utilized to camp on to DSP resources only. The DSP requirements for a voice-over-data-network call are determined and compared to a level of available DSP resources. A reservation for the required DSP resources is requested if the required DSP resources exceed the available DSP resources, and the voice-over-data-network call is established when the level of available DSP resources meets the required quantities of DSP resources.
These and other embodiments are understood from the detailed description in conjunction with the drawings below.